Ask any waitress and they will tell you that black tables are bad tippers. Not sure where this survey was done. I am in liberal MA. I’ve had this conversation with three generations of waitresses. It hasn’t changed since the 70’s.
Also liberals are awful tippers while conservatives are big tippers.
Both the DNC and RNC conventions in 2004 we held in NYC. A local radio talk show host went to both. Everywhere he ate he asked the wait staff who tipped better. All said Republicans.